Indoor Air Quality

6. Which chemicals found in indoor air are causing the most concern?

The SCHER opinion states:

3.3. Question 4

To provide a basis for assessment of risks to human health from indoor air quality, and a sound scientific basis for the development and implementation of policies, the SCHER is asked to identify potential areas of concern in relation to a) specific chemical compounds taking into account the recent outcome of the INDEX report prepared by DG JRC, b) household – chemicals and other products (e.g. decorating materials, cleaners, furnishings, etc.) and c) building dampness/moisture and microbial growth (moulds, bacteria).

The INDEX project (INDEX 2005) has evaluated health risks of
volatile chemicals in indoor air in the European
population, as a stepwise
procedure, and set up a list of
compounds with highest
concern on the basis of health impact criteria. After
consideration of the quantity and quality of all the data
available, 25 compounds were selected for a more detailed
analysis and a detailed
risk assessment was
performed for 14 of them. The highest priority chemicals were
formaldehyde, carbon monoxide, nitrogen dioxide, benzene
and
naphthalene.
SCHER agrees that these
are compounds of concern because they have caused adverse health
effects as indoor pollutants or have a high potential to cause
health effects. However, the concern is not similar in all over
in Europe due to different exposure levels. For example, limited
data on air fresheners indicate that burning of incense may
produce abnormally high benzene and formaldehyde emissions in
indoor air (Opinion of SCHER on air fresheners, SCHER
2006).

Though active smoking is excluded from this opinion, the
SCHER reminds that tobacco
smoking is the primary source of several emissions
(benzene,
fine and ultrafine
particles) indoors and associated health effects. In adults,
ETS has been associated e.g. with
coronary heart disease,
sensory irritation and exacerbation of respiratory symptoms,
including asthma (IARC
2004). In children, the association with infant
sudden death syndrome and
middle ear infections and ETS has been observed (Tamburlini et
al., 2002, DiFranza et al., 2004). The evidence clearly
indicates that ETS requires risk management.

Radon
in indoor air has been associated with lung
cancer (WHO 1998).
According to a recent analysis of European
epidemiological studies
(Darby et al., 2005) radon may be a common problem in Europe.
Radon gas diffuses through soil into residences in areas where
bedrock contains in excess
uranium. Indoor radon
concentrations can be decreased by technical means, even in
existing buildings. Data on residential radon concentrations
should be obtained by measurements in countries where such data
do not yet exist and the associated health risk assessed.

Paint-related lead still exist in indoor
environment in old houses in some EU countries though its use
has been restricted or banned in indoor paints. Children are
especially exposed through non-dietary
ingestion of the dust.
Exposure from other sources may be significant (TNO 2005)) and
the evidence is increasing that already low level exposure of
children to lead is harmful (e.g. Lanphear et al., 2005).
Therefore, it is essential to evaluate, if the lead level in
indoor environment is still a problem in EU countries. The
existing data on lead should be compiled, and thereafter, a need
for further research considered.

The indoor use of
organophosphate pesticides
for treatment of cracks and crevices (Byrne et al., 1998) or the
use of insect strips (Weis et al. 1998) may lead to high
exposures to these
compounds by
inhalation or
ingestion due to accumulation
on surfaces including children’s toys (Hore et al., 2005) and
house dust (Butte and Heinzow, 2002). This uptake may contribute
considerably to the overall uptake of
organophosphates by
children (Gurunathan et al., 1998). The acute
toxicity of organophosphate
pesticides is well known (WHO 2004b): however, it is very
unlikely that indoor levels can result in acute effects.
Recently neuro-developmental effects, have been reported both in
experimental animals (Aldridge et al., 2005 ) and
humans (Berkowitz et al., 2004) raising concern for possible
effects in children from the use of organophosphates in the
indoor environment.

Health effects (mainly sensory irritation) of
VOCs commonly found in indoor air have been
investigated in numerous studies. An extensive evaluation of all
available controlled human exposure studies by a group of
experts (Andersson et al., 1997) found that effect levels for
irritation were usually higher than concentrations in indoor
air. These studies would not explain possible health effects at
much lower concentrations reported in
epidemiological studies;
however, the exposure was not adequately measured and cause
effect relationship could not be proved due to several
confounders, such as temperature, ventilation, exposure from
other chemicals, or moulds
and mites, as well as psychosocial factors. Anderson et al.,
(1997) stated that the scientific literature is inconclusive
with respect to TVOC as a risk index. This conclusion is still
valid, when the publications since this review are taken into
account. Recent c omprehensive controlled human studies at VOC
concentrations considerably above those in normal homes show no
effects (e.g. Fiedler et al., 2005; Laumbach et al., 2005),
epidemiological studies give some indication of health effects
(e.g. Hutter et al., 2006; Saiijo et al., 2004; Takigawa et al.,
2004) but other factors than VOC may play a major role.

Several studies have reported associations between VOCs and
asthma symptoms. However, a
recent comprehensive review found no consistent association
between the commonly measured indoor VOC exposures and onset of
new asthma cases (Nielsen et al. 2007a).

Altogether, the available evidence on VOCs in causing health
effects in indoor environment is not conclusive; VOCs may also
be indicators for the presence of other stressors contributing
to health effects.

More recently reaction products formed in indoor air have been
investigated. Terpenes may react with
ozone to produce secondary
reaction products (Wolkoff et al., 2006a). Limonene reacts with
ozone and has been reported to produce both gaseous reaction
products and fine and
ultrafine particles (Wainman et al., 2000, Sarwar et al., 2004).
The highest terpene concentrations also produced high particle
levels (Sarwar et al. 2004). Several other pollutants react in
indoor air and on surfaces producing known and as yet unknown
reaction products (Weschler et al., 2006). In some studies, the
reaction products have shown irritating properties (Clausen et
al., 2001, Nøjgaard et al., 2005) and poor perceived air quality
(Tamás et al., 2006) at terpene and ozone concentrations that
can be present in indoor air. Adverse health effects have not
been observed in all studies (Laumbach et al., 2005, Fiedler et
al. 2005). Altogether, the concentrations of VOCs and ozone
causing mixture effects are as yet poorly known.

In addition to the
compounds emitted from the
intact materials in the indoor environment there may also be new
compounds formed due to
decomposition of the materials. The glue used
to fasten PVC flooring can be hydrolysed by water (dampness)
from the underlying material, especially if it is concrete with
a high pH. The compounds released from decomposing materials
should be identified and their potential health effects
evaluated.

Phthalates
are common contaminants in
the indoor environment occurring both in house dust and in
indoor air and di(2-ethylhexyl) phthalate (DEHP) is the dominant
component (Øie et al., 1997, Rudel et al., 2003, Fromme et al.,
2004). The PVC flooring material is an important source for
phthalates, but several other sources contribute in indoor
environment (Bornehag et al., 2005a). PVC products indoors
(different surface materials) have been associated with airway
effects in
epidemiological studies
(Jaakkola et al. 2006) but only in one study has the
concentrations of di(2-ethylhexyl) phthalate (DEHP) and butyl
benzyl phthalate (BBP) been measured (Bornehag et al., 2004a).
In that study DEHP was associated with
asthma and BBP with
rhinitis in children at the
highest exposure quartile (Bornehag et al., 2004a). Long-term
exposure to DEHP (Larsen et al 2007) and its metabolite,
mono-2-ethylhexyl phthalate (Hansen et al. 2007), together with
a model allergen did not
show promoting effects on the development of the allergen
specific IgE antibodies. Phthalates are not skin sensitizers for
humans and there is no evidence of respiratory sensitization
(Medeiros et al., 1999, David et al., 2003, European Union
Risk Assessment report,
2007). Based on the lack of mechanistic support and taking into
account the low exposure level of phthalates by
inhalation (Larsen et al.,
2007, Nielsen et al., 2007a), the
SCHER does not find
consistent scientific evidence which indicate that phthalates
should be high concern chemicals in indoor air. The RA report on
DEHP (European Union Risk Assessment report, 2007) suggests that
the MOSs from exposure in indoor air to reproductive effects,
which are the basis for risk characterisation, remain large
(over 200 for children, over 1000 for adults).